Anomalous magnetocaloric effects in the quasi-one-dimensional antiferromagnet BaCo${}_2$V${}_2$O${}_8$

Abstract

We investigate the transverse-field thermodynamics of the quasi-one-dimensional Ising-like antiferromagnet BaCo${}_2$V${}_2$O${}_8$, whose tilted screw-chain geometry and anisotropic Landé $g$ tensor generate spatially modulated Zeeman couplings. Angle-resolved magnetocaloric-effect (MCE) measurements reveal a high-field temperature minimum near the transverse-field Ising critical field for $H\parallel [110]$ that persists and shifts only weakly upon field rotation. Tensor-network calculations show that the rotation-induced staggered transverse field rapidly lowers the Ising critical field and that the magnetic Grüneisen ratio changes sign near the high-field temperature minimum, consistent with experiment. Our results establish that a dominant MCE response can persist away from the Ising critical region, suggesting a route to magnetic cooling by tailoring anisotropic Zeeman-coupling configurations in quantum magnets.

16 pages, 6 figures